The invention concerns a liquid filter heat exchanger unit, in particular for motor vehicles, wherein liquid is supplied to the heat exchanger by an inlet, which liquid, that after passing through the heat exchanger can be supplied through a drain of the heat exchanger to the unfiltered side of the filter element, which filter element is received in an exchangeable way in a filter housing of the liquid filter, comprising a bypass in the filter housing that connects an inlet passage for supplying the liquid to be filtered to the chamber receiving the filter element in the filter housing, wherein the bypass can be opened and closed by a switching member.
In the publication DE 102 45 005 A1 such a liquid filter heat exchanger unit is disclosed which is employed for oil cooling and oil filtering of the oil required for engine cooling. This liquid filter heat exchanger unit comprises a liquid filter with a hollow cylindrical filter element arranged in a filter housing through which the oil flows radially as well as a heat exchanger that is flanged onto the filter housing and in which the oil is cooled. The unfiltered and heated raw oil flows through an inlet passage that is provided within the filter housing first into the heat exchanger, is cooled therein, and flows out of it through an outlet opening to the unfiltered side of the filter element into a receiving chamber housing the filter element in the filter housing. The filter element is flown through radially from the exterior to the interior, subsequently the filtered raw oil flows from the filter interior axially through a drain passage out of the liquid filter heat exchanger unit and is reintroduced into the oil circulation in the engine block of the internal combustion engine.
In order to prevent clogging, in particular after a cold start, of the heat exchanger as a result of increased viscosity of the oil caused by low temperatures, a bypass branches off the inlet passage in the filter element and is connected immediately with the receiving chamber in the area of the unfiltered side of the filter element. This bypass in regular operation in which the raw oil has already reached operating temperature is closed off by a switching member embodied as a bi-metal element or a bypass valve in order to prevent direct flow of heated raw oil to the unfiltered side of the filter element by bypassing the exchanger and to guide the oil through the heat exchanger. At low temperatures however the switching member is automatically opened so that the bypass is open and the unfiltered oil can flow directly to the unfiltered side of the filter element. In this way, the heat exchanger is circumvented and an excessive pressure buildup in the lubricant circulation is prevented.
When, independent of the current temperature, the oil is to be drained from the liquid filter heat exchanger unit, for example, in order to perform an oil change, it must be ensured that only a residual volume of oil as small as possible remains within the filter or the heat exchanger.
It is an object of the invention to configure a liquid filter heat exchanger unit with constructively simple measures in such a way that a drainage as much as possible of liquid from the heat exchanger is enabled independent of the temperature.